Biomedical subjects

J L Lewis

Publications and source records attributed to J L Lewis.

At least 19 recordsLinked to original sources

PubMed2004

Evaluation of fracture toughness of cartilage by micropenetration.

Failure properties of cartilage are important in injury repair and disease, but few methods exist for measuring these properties, especially in small animals. To meet this need, a new indentation/penetration method for measuring fracture toughness of cartilage is proposed. During indentation, a conical tip is displaced into the surface of the cartilage, causing first a non-penetrating indentation, and then a penetration into the tissue. The method assumes that tissue penetration occurs during periods of "rapid work", which are identified from a curve of work rate vs. time. Total penetration depth is determined by summing the displacement during these periods. Fracture work is the work that occurs during "rapid work", or penetration, and fracture toughness defined as the fracture work divided by one-half the penetrated surface area of the indenting tip. The method was validated by indentation testing of bovine cartilage. Penetrating indentations with a conical tip were performed in bovine patellar cartilage and depth of penetration and fracture toughness predicted. For comparison with the indentation data, depth of penetration was measured in histological sections. These measurements agreed well with the predicted depth. Predicted fracture toughness also agreed with values measured via a macroscopic test. This newly described method has promise as a general method for measuring fracture toughness in cartilage, particularly in small animals, since penetrating tips with small tip radius can be manufactured and penetration may be accomplished in cartilage of minimal thickness.

Animals↗

PubMed2004

Phosphatidylinositol-3 kinase inhibitors reproduce the selective antiproliferative effects of imatinib on chronic myeloid leukaemia progenitor cells.

We investigated the role of the phosphatidylinositol-3 kinase (PI-3K) pathway in regulating the proliferation of primary chronic myeloid leukaemia (CML) progenitor cells by using imatinib to inhibit the activity of p210(Bcr-Abl). The effect of imatinib on the expression of PI-3K pathway proteins was investigated by kinase assays and Western blotting; PI-3K was inhibited by wortmannin or LY294002, Jak2 by AG490 and farnesylation by FTI II; progenitor cell proliferation (self-renewal) was measured by growing myeloid colonies in vitro, then replating them to observe secondary colony formation. Suppression of p210(Bcr-Abl) with imatinib indirectly suppressed the activity of PI-3K and its downstream targets (Erk, Akt and p70S6 kinase), thereby implicating the PI-3K pathway in p210(Bcr-Abl)-mediated signalling in primary CML progenitor cells. The PI-3K inhibitors, wortmannin and LY294002 reproduced the differential effects of imatinib on normal and CML progenitor cell proliferation in vitro by increasing normal cell (P = 0.001) and reducing CML cell proliferation (P = 0.0003). This differential effect was attributable to dysregulated signalling by granulocyte colony-stimulating factor in CML. The responses of individual patient's cells to wortmannin correlated with their responses to imatinib (P = 0.004) but not their responses to AG490 (Jak2 kinase inhibitor) or FTI II (farnesyltransferase inhibitor). Individual responses to wortmannin also correlated with responses to interferon alpha (IFNalpha) (P = 0.016). Imatinib-resistant K562 cells were sensitive to LY294002. Inhibition of the PI-3K pathway may be common to imatinib and IFNalpha and reflect dysregulated cytokine signalling. As imatinib-resistant cells remained sensitive to wortmannin and LY294002, targeting the PI-3K pathway may provide an alternative therapy for imatinib-resistant patients.

Alkyl and Aryl Transferases↗

PubMed2003

Effect of specimen thickness on fracture toughness of bovine patellar cartilage.

Fracture toughness and crack tip opening angle were measured for bovine patellar cartilage using modified single-edged notch specimens of two thicknesses. There was no difference in fracture toughness between thin (0.7 mm) versus relatively thick (2.7 mm) specimens, but the crack tip opening angle at initiation of crack propagation was larger for the thin specimens (106 deg) than for the thick specimens (70 deg). Fracture toughness of the bovine patellar cartilage (1.03 kJ/m2) was not statistically different than that reported previously for canine patellar cartilage (1.07 kJ/m2) employing the same methods. Large variation in measurements for both bovine and canine cartilage are in part attributable to variation between individual animals, and are consistent with variation in other mechanical property measurements for articular cartilage. The observed reduction in crack tip opening angle with increased specimen thickness is consistent with behavior of some engineering materials, and demonstrates that specimen thickness influences fracture behavior for bovine patellar cartilage.

Animals↗

PubMed2001

The influence of INK4 proteins on growth and self-renewal kinetics of hematopoietic progenitor cells.

This study investigated the influence of expression of proteins of the INK4 family, particularly p16, on the growth and self-renewal kinetics of hematopoietic cells. First, retrovirus-mediated gene transfer (RMGT) was used to restore p16(INK4a) expression in the p16(INK4a)-deficient lymphoid and myeloid cell lines BV173 and K562, and it was confirmed that this inhibited their growth. Second, to sequester p16(INK4a) and related INK4 proteins, cyclin-dependent kinase 4 (CDK4) was retrovirally transduced into normal human CD34(+) bone marrow cells and then cultured in myeloid colony-forming cell (CFC) assays. The growth of CDK4-transduced colonies was more rapid; the cell-doubling time was reduced; and, upon replating, the colonies produced greater yields of secondary colonies than mock-untransduced controls. Third, colony formation was compared by marrow cells from p16(INK4a-/-) mice and wild-type mice. The results from p16(INK4a-/-) marrow were similar to those from CDK4-transduced human CFCs, in terms of growth rate and replating ability, and were partially reversed by RMGT of p16(INK4a). Lines of immature granulocytic cells were raised from 15 individual colonies grown from the marrow of p16(INK4a-/-) mice. These had a high colony-forming ability (15%) and replating efficiency (96.7%). The p16(INK4a-/-) cell lines readily became growth factor-independent upon cytokine deprivation. Taken together, these results demonstrate that loss of INK4 proteins, in particular p16(INK4a), increases the growth rate of myeloid colonies in vitro and, more importantly, confers an increased ability for clonal expansion on hematopoietic progenitor cells.

Animals↗

PubMed2001

BCR-ABL and interleukin 3 promote haematopoietic cell proliferation and survival through modulation of cyclin D2 and p27Kip1 expression.

Although it is evident that BCR-ABL can rescue cytokine-deprived hematopoietic progenitor cells from cell cycle arrest and apoptosis, the exact mechanism of action of BCR/ABL and interleukin (IL)-3 to promote proliferation and survival has not been established. Using the pro-B cell line BaF3 and a BaF3 cell line stably overexpressing BCR-ABL (BaF3-p210), we investigated the proliferative signals derived from BCR-ABL and IL-3. The results indicate that both IL-3 and BCR-ABL target the expression of cyclin Ds and down-regulation of p27(Kip1) to mediate pRB-related pocket protein phosphorylation, E2F activation, and thus S phase progression. These findings were further confirmed in a BaF3 cell line (TonB.210) where the BCR-ABL expression is inducible by doxycyclin and by using the drug STI571 to inactivate BCR-ABL activity in BaF3-p210. To establish the functional significance of cyclin D2 and p27(Kip1) expression in response to IL-3 and BCR-ABL expression, we studied the effects of ectopic expression of cyclin D2 and p27(Kip1) on cell proliferation and survival. Our results demonstrate that both cyclin D2 and p27(Kip1) have a role in BaF3 cell proliferation and survival, as ectopic expression of cyclin D2 is sufficient to abolish the cell cycle arrest and apoptosis induced by IL-3 withdrawal or by BCR-ABL inactivation, while overexpression of p27(Kip1) can cause cell cycle arrest and apoptosis in the BaF3 cells. Furthermore, our data also suggest that cyclin D2 functions upstream of p27(Kip1), cyclin E, and cyclin D3, and therefore, plays an essential part in integrating the signals from IL-3 and BCR-ABL with the pRB/E2F pathway.

Animals↗

PubMed2001

The transmembrane domain of syntaxin 1A is critical for cytoplasmic domain protein-protein interactions.

Assembly of the plasma membrane proteins syntaxin 1A and SNAP-25 with the vesicle protein synaptobrevin is a critical step in neuronal exocytosis. Syntaxin is anchored to the inner face of presynaptic plasma membrane via a single C-terminal membrane-spanning domain. Here we report that this transmembrane domain plays a critical role in a wide range of syntaxin protein-protein interactions. Truncations or deletions of the membrane-spanning domain reduce synaptotagmin, alpha/beta-SNAP, and synaptobrevin binding. In contrast, deletion of the transmembrane domain potentiates SNAP-25 and rbSec1A/nsec-1/munc18 binding. Normal partner protein binding activity of the isolated cytoplasmic domain could be "rescued" by fusion to the transmembrane segments of synaptobrevin and to a lesser extent, synaptotagmin. However, efficient rescue was not achieved by replacing deleted transmembrane segments with corresponding lengths of other hydrophobic amino acids. Mutations reported to diminish the dimerization of the transmembrane domain of syntaxin did not impair the interaction of full-length syntaxin with other proteins. Finally, we observed that membrane insertion and wild-type interactions with interacting proteins are not correlated. We conclude that the transmembrane domain, via a length-dependent and sequence-specific mechanism, affects the ability of the cytoplasmic domain to engage other proteins.

Animals↗

PubMed2001

Olfactory bulb uptake and determination of biotransfer factors in the California ground squirrel (Spermophilus beecheyi) exposed to manganese and cadmium in environmental habitats.

Manganese (Mn) and cadmium (Cd) profiles in olfactory bulbs of California ground squirrels (Spermophilus beecheyi) trapped at Lawrence Livermore National Laboratory's Site 300 facility in California were determined with proton induced X-ray emission (PIXE). As a reference, Mn profiles in olfactory bulbs from laboratory rats exposed via nose-only inhalation to 0.53 mg/m3 Mn in the form of MnCl2 were also determined with PIXE. Atomic absorption spectrophotometry was used to measure soil Mn and Cd contents from the trapping sites and Mn and Cd contents in ground squirrel liver and leg muscle tissues. The data from laboratory rats revealed that Mn uptake into the olfactory bulb occurs via inhalation exposure. Data from ground squirrels and knowledge of the collection sites indicate that although several routes of exposure may occur, fossorial rodent olfactory uptake affords a significant exposure route to Mn and Cd in soils. Measured biotransfer factors (ratio of leg muscle tissue metal content to soil metal content) for Cd in ground squirrels were 10(3)-fold greater than exposure modeling estimates based on oral Cd uptake data from livestock. The measurements for ground squirrel tissues show that when conducting ecological risk assessments for natural habitats considerable care should be taken in selecting transfer factors. Specifically, transfer factors derived from data pertaining to comparable exposure pathways and ecological setting should be used wherever possible.

Animals↗

PubMed2001

Neoadjuvant therapy for adenocarcinoma of the rectum: tumor response and acute toxicity.

PURPOSE: This study was designed to evaluate the down-staging effect and acute toxicity of preoperative radiation and chemoradiation for primary adenocarcinoma of the rectum. METHODS: The results of pretreatment staging with transrectal ultrasound and computed tomography were compared with final histologic stage in 260 consecutive patients who underwent neoadjuvant therapy and proctectomy for primary adenocarcinoma of the rectum. Patients underwent short-course radiation (2,000 cGy in five fractions), long-course radiation (4,500 cGy in 25 fractions), or chemoradiation (4,500 cGy in 25 fractions with concurrent chemotherapy). RESULTS: Down-staging of one or more T stages occurred in 116 of 260 (45 percent) patients overall (short-course radiation 34/82 (42 percent), long-course radiation 55/122 (45 percent), chemoradiation 27/56 (48 percent), P = not significant). Down-staging of one or more N stages occurred in 85 of 178 (48 percent) patients overall (short-course radiation 12/45 (27 percent), long-course radiation 49/86 (57 percent), chemoradiation 24/47 (51 percent), P = 0.003). Complete pathologic response was observed in 16 of 260 (6 percent) patients overall (short-course radiation 4/82 (5 percent), long-course radiation 5/122 (4 percent), chemoradiation 7/56 (13 percent), P = 0.08). Resection with negative margins (distal, proximal, and radial) was achieved in 211 of 227 patients (93 percent) in whom complete radial margin data were available. Permanent stomas were created in 35 percent of patients; temporary stomas were created in 15 percent. Thirty-three Grade 3 or 4 toxicities occurred in 22 of 260 (8 percent) patients overall during neoadjuvant therapy. Toxicity was more frequent in patients receiving chemoradiation (14/56; 25 percent) and long-course radiation (8/122; 7 percent) than in those receiving short-course radiation (0/82; 0 percent), P < 0.0001. Perioperative complications occurred in 93 patients overall (36 percent). The postoperative mortality rate was 0.4 percent (1/260). There was no significant difference in the complication rate between patients treated with short-course radiation (26/82; 32 percent), long-course radiation (46/122; 36 percent), and chemoradiation (21/56; 38 percent). CONCLUSION: Neoadjuvant therapy for adenocarcinoma of the rectum is well tolerated and can produce substantial down-staging and a high curative resection rate. Chemoradiation can achieve high complete pathologic response rates, although toxicity during neoadjuvant therapy is greater than for radiation alone. Short-course radiation can achieve down-staging of both T stage and N stage.

Adenocarcinoma↗

PubMed2001

Progenitor cells from patients with advanced phase chronic myeloid leukaemia respond to STI571 in vitro and in vivo.

STI571 targets p210(BCR-ABL) in chronic myeloid leukaemia (CML). In vitro, STI571 reduces self-replication (replating ability) by chronic-phase CML CFU-GM. Here, we studied CFU-GM in advanced-phase (accelerated and blast crisis) CML. The numbers and self-replication of CFU-GM in advanced phase were greater than in the chronic phase. Self-replication by CFU-GM from advanced phase patients was reduced by STI571 or IFN alfa to the same extent as in the chronic phase. The reduced replating ability induced by STI571 correlated with that induced by IFN alpha (r=0.73). STI571 treatment in vivo also reduced replating ability and the numbers of CFU-GM/ml of blood.

Antineoplastic Agents↗

PubMed2001

Peripheral blood progenitor cell mobilisation alters myeloid, but not erythroid, progenitor cell self-renewal kinetics.

Transplantation of progenitor cells which have been mobilised into the bloodstream (PBPC) following the administration of G-CSF results in more rapid neutrophil recovery than transplantation of bone marrow (BM). The reasons for the accelerated neutrophil engraftment are not clear, but would be explained by increased self-replication of myeloid progenitor cells (CFU-GM). We have used a CFU-GM replating assay to investigate myeloid progenitor self-replication, and quantification of subcolony formation during erythroid burst formation to quantify erythroid progenitor self-renewal. Secondary colony formation by CFU-GM, grown from PBPC and then replated was increased compared with secondary colony formation by BM CFU-GM (P = 0.0001); erythroid subcolony formation was not altered. There was no difference between the replating abilities of PBPC CFU-GM derived from allogeneic donors (normal individuals) and autologous donors (patients with malignant disease) although differences were found between subgroups of autologous donors. The increased replication of PBPC could not be accounted for by a reduction in progenitor cell apoptosis; PBPC CFU-GM contained slightly fewer apoptotic CD34+ cells than BM CFU-GM. The increased replication by PBPC CFU-GM was reversible because it declined when CFU-GM colonies were passaged through three sequential CFU-GM replating cycles. This decline in self-replication was more rapid than the decline seen in replated BM CFU-GM. The self-replication of PBPC CFU-GM, and subcolony formation by BFU-E could be further enhanced by exposure to cytokines in vitro. We conclude that mobilisation alters the replication kinetics of myeloid, but not of erythroid, progenitor cells, that mobilisation-induced events are of limited duration and that in vitro exposure to cytokines may modify PBPC progenitor cell kinetics.

Blood Cells↗

PubMed2001

Collagen architecture and failure processes in bovine patellar cartilage.

Cartilage fails by fibrillation and wearing away. This study was designed to identify the microscopic failure processes in the collagen network of bovine cartilage using scanning electron microscopy. Cartilage samples from fibrillated cartilage from the bovine patella were removed from the bone, fixed, digested to remove proteoglycans, freeze-fractured, and processed for SEM. The architecture of the collagen network in the normal cartilage was first defined, and then the failure processes were identified by examining sites of fibrillation and at crack tips. The bovine patellar cartilage was organised with a superficial layer composed of 3-5 lamina, attached to a sub-superficial tissue by angled bridging fibrils. Collagen in the sub-superficial tissue was organised in lamina oriented in the radial direction up to the transition zone. Failure of the system occurred by cracks forming in superficial layer and lamina, creating flaps of lamina that rolled up into the larger 'fronds'. Larger cracks not following the laminar planes occurred in the transition, mid, and deep zones. Failure at the crack tips in the sub-superficial tissue appeared to be by peeling of collagen fibrils, as opposed to breaking of collagen fibrils, suggesting a 'glue' bonding the collagen fibrils in a parallel fashion. Cracks propagated by breaking these bonds. This bond could be a site of disease action, since weakening of the bond would accelerate crack propagation.

Animals↗

PubMed2001

Depression and blood types.

A sample of 108 normal volunteers (grouped as blood Types O, A, and B/AB) were administered the Beck Depression Inventory. The results suggest that the association between depression and blood Type O that has been found for hospitalized patients can also be observed in normal patients.

ABO Blood-Group System↗

PubMed2001

The benefit of a special elective gynecologic oncology program for obstetrics and gynecology residents.

OBJECTIVE: To assess the benefit of a special elective gynecologic oncology program for Obstetrics and Gynecology (Ob/Gyn) residents. METHODS: We reviewed our housestaff records from July 1992 to June 1998 and the National Residency Matching Program (NRMP) subspeciality match results for gynecologic oncology from its inception in 1994 to 1999. RESULTS: From July 1992 to June 1998, a total of 146 residents participated in our elective program. Of the 104 candidates who went through our program and subsequently participated in the NRMP, 55 (53%) obtained match positions. After completion of the elective, 42 of the 146 residents (29%) did not participate in the NRMP for gynecologic oncology and therefore were not eligible to obtain match appointments. During the study period, there were 255 other residents in the United States who applied for gynecologic oncology fellowship positions through the NRMP and did not participate in our program. Of these 255 candidates, 137 (54%) matched. CONCLUSION: The percentage of residents who went through our program, participated in the NRMP, and obtained fellowships did not differ significantly from the percentage of residents who matched without participating in the program. However, almost one-third of the residents who went through our program did not participate in the NRMP. The reasons for their lack of participation were not formally evaluated, but are likely related to a personal decision to pursue another carrer pathway, a decision facilitiated by their experience in our program. Therefore, it appears that the main benefits of the program are to help potential candidates decide whether or not to pursue a career in gyencologic oncology and to aid fellowship programs in identifying exceptional candidates for subspecialty training.

Fellowships and Scholarships↗

PubMed2000

Membrane-embedded synaptotagmin penetrates cis or trans target membranes and clusters via a novel mechanism.

The synaptic vesicle protein synaptotagmin I has been proposed to serve as a Ca(2+) sensor for rapid exocytosis. Synaptotagmin spans the vesicle membrane once and possesses a cytoplasmic domain largely comprised of two C2 domains designated C2A and C2B. We have determined how deep the Ca(2+)-binding loops of Ca(2+).C2A penetrate into the lipid bilayer and report mutations in synaptotagmin that can uncouple membrane penetration from Ca(2+)-triggered interactions with the SNARE complex. To determine whether C2A penetrates into the vesicle ("cis") or plasma ("trans") membrane, we reconstituted a fragment of synaptotagmin that includes the membrane-spanning and C2A domain (C2A-TMR) into proteoliposomes. Kinetics experiments revealed that cis interactions are rapid (< or =500 micros). Binding in the trans mode was distinguished by the slow diffusion of trans target vesicles. Both modes of binding were observed, indicating that the linker between the membrane anchor and C2A domain functions as a flexible tether. C2A-TMR assembled into oligomers via a novel N-terminal oligomerization domain suggesting that synaptotagmin may form clusters on the surface of synaptic vesicles. This novel mode of clustering may allow for rapid Ca(2+)-triggered oligomerization of the protein via the membrane distal C2B domain.

Acrylamide↗

PubMed2000

A simple cryopreservation method for the maintenance of cell viability and mechanical integrity of a cultured cartilage analog.

A method for cryopreserving a 100-microm-thick sheet of tissue produced by cultured rabbit chondrocytes has been developed. The method maintains cell viability and avoids tissue fracture and degradation of mechanical properties. A slow-freeze, fast-thaw procedure with 2 M Me(2)SO as the cryoprotectant resulted in no tissue fracture and approximately 90% viable cells after storage in culture flasks at -80 degrees C. The cells in the retrieved tissue remained responsive to IL-1beta, and tensile and fracture toughness properties of the tissue were not degraded by cryopreservation.

Animals↗

PubMed2000

Contact-mediated inhibition of human haematopoietic progenitor cell proliferation may be conferred by stem cell antigen, CD34.

INTRODUCTION: The function of CD34, a transmembrane sialomucin expressed by human haematopoietic progenitor cells, is poorly understood. Its structure suggests it may act as a cell adhesion and signalling molecule. MATERIALS AND METHODS: KGIa cells and primary CD34-positive marrow cells were tested for their ability to aggregate in the presence of the anti-CD34 antibody QBEND10; CFU-GM colonies were grown using standard methods and tested for their content of colony-forming cells by replating; 'haematons' were isolated from marrow by filtration; the phosphorylation of CD34 was investigated by immunoprecipitation and Western blotting DISCUSSION: CD34-positive cells in human bone marrow, like KG1a cells, aggregate when incubated with QBEND10. Staining aggregates with anti-CD34-FITC revealed that aggregation involved co-localisation of CD34 at intercellular binding sites. We examined myeloid colonies (CFU-GM) grown from normal human bone marrow cells, and multicellular aggregates ('haematons') separated from freshly aspirated marrow by filtration, and found CD34-positive cells bound together with co-localisation of the CD34 at the binding sites. This finding shows that CD34-positive cell-cell adhesion occurs physiologically in vitro and in vivo. QBEND10-induced aggregation of KG1a and CD34-positive cells was enhanced by staurosporine (a protein kinase C inhibitor) and inhibited by genistein (a protein tyrosine kinase inhibitor). Moreover, aggregated cells had increased phosphorylation of tyrosine on CD34 and translocation of protein kinase C (PKC) to the cytoplasm, compared with non-aggregated cells. We used the ability of primary colonies to produce secondary colonies on replating as a functional parameter and found that the replating ability of the colonies was increased by treatment with genistein (P=0.003). In addition, the ability of individual samples of primary CD34-positive cells to undergo QBEND10-induced aggregation and the ability of CD34-positive cell-derived colonies to produce secondary clones on replating were inversely related (r=0.86). CONCLUSION: Our results suggest that homotypic aggregation of haematopoietic progenitor cells may be an important mechanism for preventing inappropriate proliferation in vivo. Thus, regulation of expression of the CD34 molecule may play an important role in maintaining the normal level of haematopoietic activity by contact-mediated inhibition of progenitor cell proliferation.

Antibodies, Monoclonal↗

PubMed2000

Distal radial metaphyseal forces in an extrinsic grip model: implications for postfracture rehabilitation.

The purpose of this study was to establish the relationship between force at the distal radius and power grip force of the hand, a common functional and rehabilitation maneuver. This information will provide limits of allowable grip forces during postfixation rehabilitation and guide design requirements for fixation systems. By designing a model of power grip using the extrinsic hand musculotendinous units, we were able to compare grip force with force at the distal radius. Our results show that to obtain 10 N of grip force, approximately 26.3 N of force is transmitted through the distal radius, 52.4 N is transmitted through the radius and ulna combined, and 30.0 N needs to be applied to the flexor tendons. Fifty-one percent of the total forearm force was transmitted through the distal radius in this model. If all forearm forces were transmitted through the radius, 52 N of force would be transmitted through the distal radius to obtain 10 N of grip force. The clinical application of this model suggests that since failure forces of tested distal radius fixation systems range from 55 to 825 N, rehabilitation grip force should not exceed 10 to 159 N, depending on the type of fixation.

Biomechanical Phenomena↗

PubMed1999

A composites theory predicts the dependence of stiffness of cartilage culture tissues on collagen volume fraction.

The tensile stiffness of tissue grown from chondrocyte culture was both measured experimentally and predicted using a composites model theory relating tissue microstructure to macroscopic material stiffness. The tissue was altered by several treatment protocols to provide a wide range of collagen fibril volume fraction (0.015-0.15). The rate of change of tissue modulus with change in collagen volume fraction predicted by the theory was within 14% of the slope of the linear fit through the experimental data, without the use of fitting parameters for the theoretical value of the slope. Use of the model to simulate cytokine mediated tissue digestion suggests that the action of IL-1beta and retinoic acid is mainly removal of proteoglycans and some removal of collagen. The model also indicates that the matrix and collagen remaining in the tissue has the same elastic properties as the untreated tissue, and is not damaged due to the alteration. Young's modulus of the collagen fibrils is predicted to be 120 MPa, a value in the range of previous studies. This value is dependent mainly on the matrix modulus and collagen fibril volume fraction and not on Poisson's ratio of either matrix or fibril. Poisson's ratio of the tissue depends primarily on the Poisson's ratio of the matrix.

Animals↗